Barca struggled in front of goal in the disappointing stalemate at the Camp Nou last weekend and face a tricky trip to Real Sociedad on Sunday.
Robert Lewandowski, Raphinha and Andreas Christensen all made their debuts from the start against Rayo and Franck Kessie made his first competitive appearance for the club as a substitute.
Barcelona, who have struggled financially in the last two years, are also waiting to be able to register France defender Jules Kounde after his arrival from Sevilla.
But Xavi has called for calm from supporters as he looks to bed in the new players.
“I understand the disappointment, the expectations are really high,” Xavi said after the Rayo game.
“We will have to analyse the game, improve and continue to believe in the style of play.
“Rayo defended well. It was harder for us to create than usual.
“It’s a shame because we wanted to show the fans that we are on the right track. It is disappointing, but we ask for patience and for people to believe in this team.”
Xavi helped turn the Catalan giants’ fortunes around last season, leading them to a second-placed finish after taking over with their top-four hopes in doubt.
Barca still ended 13 points adrift of champions Real Madrid, who started their title defence with a come-from-behind victory at Almeria.
Carlo Ancelotti’s Champions League winners play their second straight away game, taking on Celta Vigo on Saturday.
Real trailed newly-promoted Almeria for much of their first match of the campaign until Lucas Vazquez’s equaliser, before David Alaba came off the bench to score the winner with his first touch from a free-kick.
The most impressive performance from one of the title hopefuls came from Atletico Madrid.
Alvaro Morata scored twice in a comfortable 3-0 win at Getafe as Diego Simeone’s side, who won the title in 2021, laid down an early marker.
The Spain striker, who spent the past two seasons on loan at Juventus, has been linked with a possible move away from the Estadio Metropolitano, with Manchester United reportedly interested.
“Everyone at the club hopes he continues,” said Simeone.
“He is working very well, in an extraordinary way. I think that all footballers need to have confidence to do important things.
“He came back with great humility and wanting to work.”
Atletico host Villarreal, who also won 3-0 last weekend against Real Valladolid, on Sunday.
Player to watch: Takefusa Kubo
Japan’s Kubo marked his debut for Real Sociedad with the only goal in their victory at Cadiz last week. The 21-year-old was signed from Real Madrid last month after loan spells at Real Mallorca, Villarreal and Getafe. Kubo will be hoping to impress on Sunday against Barcelona, where he featured as a youth player.
7: Visits since Barcelona last lost at Real Sociedad, having previously gone eight games without a victory in San Sebastian.
3: New Sevilla signing Tanguy Nianzou could become only the third player born in the 21st century to play in three of Europe’s top five leagues, after Moise Kean and Ethan Ampadu.
Fixtures (all times GMT)
Espanyol v Rayo Vallecano (1800), Sevilla v Real Valladolid (2000)
Osasuna v Cadiz (1530), Real Mallorca v Real Betis (1730), Celta Vigo v Real Madrid (2000)
Athletic Bilbao v Valencia (1530), Atletico Madrid v Villarreal (1730), Real Sociedad v Barcelona (2000)
Elche v Almeria (1800), Girona v Getafe (2000)